Conventional computer systems, such as personal computer systems, generally utilize a hierarchical architecture having several levels. The highest level, which is generally connected to a processor through a processor bus, is a system controller or the like. The system controller includes a memory controller that is connected to system memory, which is generally implemented using dynamic random access memory (“DRAM”) devices. The system controller also serves as a bridge, sometimes known as a “North Bridge,” to a peripheral bus, such as a peripheral component interface (“PCI”) bus. Peripheral components such as hard disk drives, Ethernet interfaces, and the like may be connected to this peripheral bus. A second bus bridge, sometimes known as a “South Bridge,” is sometimes used to connect the first peripheral bus to a second peripheral bus, such as an LPC (Low Pin Count) bus. Input/output devices such as keyboards, mice, serial and parallel ports are commonly connected to this bus.
Hard disk drives are typically used in computer systems to store a large volume of data and instructions. Hard disk drives have the advantage of being non-volatile so that data stored in the disk drive are not lost when power is removed from the system. However, hard disk drives also have certain disadvantages. For example, it can require a considerable amount of power to keep hard disk drives powered so they can be available to access data more quickly. Also, since accessing data stored in a hard disk drive normally requires physical movement of a read/write head, the latency period for accessing data can be considerable. To minimize these and other limitations of hard disk drives, proposals have been made to incorporate a small amount of solid state non-volatile memory, such as flash memory devices, in hard disk drives. Using flash memory devices provides several advantages, including lower power consumption, faster access times, and increased reliability.
Although placing flash memory devices in hard disk drives does provide several advantages, these advantages come with a price and are less advantageous than they might be. Specifically, there is a great deal of price competition in the sale of computer system components in general and hard disk drives in particular. Including flash memory devices or other non-volatile memory devices in hard disk drives may increase the price of such hard disk drives to unacceptable levels. This price competition is also likely to keep the amount of flash memory on the hard drive low, and therefore provide limited benefit. Also, although the use of flash memory devices in hard disk drives can significantly reduce the latency of accessing stored data and instructions, the latency and data bandwidth are still limited by the need to couple the data and instructions through one or more bus bridges to the hierarchy level of the hard disk drive.
There is therefore a need for a computer system and method that uses non-volatile memory devices to perform functions typically performed by hard disk drives, but does so in a manner that avoids some of the disadvantages and limitations of conventional hard disk drives incorporating non-volatile memory devices.